Gravity Field Energy Storage and Recovery System

ABSTRACT

Invention defines a method and apparatus for storing energy where a power source is used to reposition a mass in a gravitational field to a position of higher potential energy where the stored potential energy may be recovered with extremely low loss regardless of the state of charge of the system, where the force of gravity may be allowed to accelerates the mass, where the resulting kinetic energy is converted to shaft horsepower. Said shaft horsepower may be converted to pneumatic, electrical, or hydraulic power. A variation defines a method where a power source is used to submerge a buoyant object in a fluid, where the submerged object represents a potential energy, where the force of gravity via the fluid, displaces the submerged buoyant object, where the kinetic energy resulting from the displacement is converted to shaft horsepower. Said shaft horsepower may be similarly converted to pneumatic, electrical, or hydraulic power. Invention defines a process where available energy can be used to do work to raise a massive object against a planetary gravitational field, to a position of high potential energy which can be maintained indefinitely. On demand the mass can be accelerated by the gravitational field and converted to kinetic energy, which is harnessed and converted to shaft horsepower, allowing the desired energy recovery from the energy storage system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Significant advances have been made in alternative energy systems as society seeks to ameliorate the deleterious effects inherent in legacy energy systems. Fossil fuel systems rely on the combustion of hydrocarbons such as ethane, n-pentane, methane, n-octane, and coal, which, under perfect conditions, will produce heat and kinetic energy and the by-products of water and carbon dioxide. As an example, the combustion of methane in the presence of air is stoichiometric as

CH₄+2(O₂+3.76N₂)→CO₂+2H₂O+7.52N₂

An array of hydrocarbons that are the constituents of gasoline (a well-known example is n-octane), as well as the hydrocarbons associated with coal and fuel oil, all burn in a similar fashion. Automobile engines rely on the Carnot cycle and gas turbines, powering jet aircraft and marine propulsion, rely on the Brayton cycle to harness, through a mechanical arrangement, the rapid gas expansion of the burning fuel to develop continuous shaft horsepower.

Commercial electric power is produced when coal or fuel oil is burned to boil water, the steam being used to turn a turbine as per the Rankine cycle, producing a continuous shaft horsepower. Nuclear electric power generation utilizes a controlled nuclear fission of uranium and it's byproducts as a heat source to boil water, and similarly, develops a continuous shaft horsepower from a steam turbine. In both cases, the continuous shaft horsepower is used to rotate an electric generator.

The problems associated with our legacy systems dominate our technological, economic, strategic, scientific, and geopolitical landscapes. An energy hungry world seeks to control the world's precious hydrocarbon resources resulting in “blood for oil” military conflicts which themselves carry a risk of escalation to a global scope, raising the terrible specter of exchanged nuclear strikes between states equipped with atomic weapons.

The use of hydrocarbons as a fuel, even under perfect conditions, emits carbon dioxide as a byproduct, which as a “greenhouse gas” is implicated in global warming.¹ Rarely are the conditions perfect however, and the burning of hydrocarbon emits many unfortunate byproducts which otherwise pollute the air, causing serious human health problems. ¹ http://www.globalchange.gov/

Nuclear electric power generation has the advantage that it emits no greenhouse gases. There are, however, a number of thorny problems associated with nuclear power. The mining, refining, and processing of uranium ore into a useable material, is an environmentally costly process with associated health risks.² The operation of nuclear power stations is not foolproof as the disasters at Three Mile Island, Chernobyl, and Fukushima, demonstrate. The operation of nuclear power reactors produces a plethora of fission products associated with the spent nuclear fuel. Nuclear waste disposal involves the processing, transportation, and storage of these fission products. This presents an ongoing national problem involving challenging technological, scientific, strategic, and political issues.³ Moreover, spent nuclear fuel presents a security risk, as the proliferation of fissile materials can present opportunities to “rogue states” to obtain weapons grade nuclear materials. ² http://www.gjem.energy.gov/moab/³ http://www.energy.gov/photos/yucca-mountain

The development and deployment of alternative energy systems beyond the legacy systems has the potential to alleviate many of the above problems. Light energy from the Sun striking the Earth is a far greater potential source of energy than all of the world's proven oil reserves. But new challenges arise due to the nature of the alternative systems.

Many of the alternative energy systems are not continuous systems but are time-varying as they only generate power when the alternative energy source is available. Solar powered photovoltaic cells produce appreciable power only when sufficient sunshine is available. Wind generators produce power only when the wind is blowing. Tidal water systems generate energy only when the water is moving, etc. This non-continuous, or periodic power harvesting technology requires massive energy storage systems to transform the periodic energy pulses to a quasi-continuous system to meet society's demand.

2. Description of Related Art

Each of the periodic alternative energy systems rely on an energy storage system to capture the excess energy and deliver it when required. A typical alternative energy system will generate electrical energy. Solar photovoltaic cells, wind generators, tidal and wave generators will use batteries and a battery charging system to store excess electrical energy. When required, the batteries will be switched from charging mode into discharging mode to apply the stored electrical energy. The delivered electrical energy is in the form of Direct Current (DC) electrical energy and may require the use of DC to DC converters and DC to AC (Alternating Current) inverters to deliver the stored energy in a form that is directly usable.

These periodic alternative energy systems then, rely on the added complexity and expenses related to energy conversion and chemical battery storage technologies. Chemical Batteries suffer from low energy/power density, poor low-temperature performance, limited cycle life, intrinsic safety limitations, and high cost.

An important consideration in any energy conversion technology is the efficiency of the system which describes the losses inherent in the conversion. Lead acid batteries are commonly used in small photo voltaic systems. Sandia National Laboratories studied lead acid battery efficiencies and found that efficiencies are as low as 50% if the battery is at a high rate of charge when charging begins. Also, partial charging is deleterious to the battery itself:

-   -   This result has important implications to operational PV         systems. That is, if a battery is partially charged for several         consecutive cycles (for example, the array is marginally sized         and there is a series of less than full sun days in the winter)         the useable battery capacity decreases each cycle, even though         the same amount of energy has been presented to the battery each         day. This is the result of battery inefficiencies, electrolyte         stratification, and sulfate buildup during these partial         charges.⁴ ⁴A Study of Lead-Acid Battery Efficiency Near         Top-of-Charge and the Impact on PV System Design

Thus, time-varying alternative energy systems rely upon a storage technology which is inherently inefficient and problematical from an operational, financial, and design standpoint. What is required is an alternative energy storage system that does not require batteries. The Gravity Field Energy Storage & Recovery System Invention is designed to deliver this alternative solution.

SUMMARY OF THE INVENTION

The Gravity Field Energy Storage & Recovery System [GFESRS] invention is a mechanical, electrical and electronic system that has the ability to harness any electrical or mechanical power source and allow it to do work to configure a mechanical system into a state of high potential energy, using either a hi-mass object in a gravitational field or a large buoyant object submerged into a fluid.

The charging cycle consists of repositioning a massive object in a gravity field to a position of higher potential energy. The potential energy can be stored without loss for extended periods of time.

The potential energy stored in the invention can be recovered on demand. The energy recovery mode consists of releasing the massive object in the gravity field in a controlled fall, producing a kinetic energy which can then be transformed into a useable form of energy such as electricity, pneumatic, or hydraulic power.

The work done to elevate the mass in the gravitational field then, is manifested as potential energy. The potential energy is stored indefinitely as long as the mechanism is in working order. This energy storage technique will not lose any potential energy over time as many other energy storage systems will.

When the system requires the stored potential energy to be released and recovered, the energy recovery cycle is activated. The mass suspended in a gravitational field is coupled to an apparatus that can convert the stored potential energy. The locking mechanism is released and allows the force of gravity to deliver a controlled acceleration of the mass towards the center of gravity. As the mass is accelerated in the gravitational field, the energy conversion apparatus, converts the kinetic energy into a form that can perform the useful work that system requires.

The present invention works the same in the context of a fluid whether the fluid is gas or liquid. Typically, the mass is denser than the surrounding fluid and energy is recovered in a controlled fall. This is the case if the mass is in air or water. This method would also work in a vacuum. If the mass is less dense than the surrounding fluid, it would be buoyant and tend to “float.” In such a case, mechanical energy can be stored by forcing the mass to submerge into the fluid. The energy can be recovered by allowing the mass to float, recovering the energy as the mass displaces upward. This would apply to a buoyant object in water, or a lighter than air vessel or dirigible. Forcing the dirigible toward the center of the earth would be to reposition it to a position of higher potential energy. This energy can be recovered in a “controlled float” as the tethered dirigible rises in the atmosphere. Forcing a buoyant object in water to submerge stores energy which can be recovered as the object is allowed to rise.

Thus, a buoyant object can be repositioned to a position of higher potential energy by forcing it to submerge into a fluid and can be used to store energy. The energy storage can be released on demand, producing a kinetic energy which can then be transformed into a useable form of energy such as electricity, pneumatic, or hydraulic power. Thus a massive object can be repositioned to a position of higher potential energy by raising its altitude and can be used to store energy. The energy storage can be released on demand, producing a kinetic energy which can then be transformed into a useable form of energy such as electricity, pneumatic, or hydraulic power.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1) Shows the complete invention using a solar array as the power source.

FIG. 2) Shows the invention as it could be installed in an elevator shaft in a high-rise building.

FIG. 3) Shows the invention as it could be installed on an offshore oil platform using a buoyant object.

FIG. 4) Shows the invention as it could be installed in an oil field using a diesel tractor with power takeoff as energy source.

DETAILED DESCRIPTION OF THE INVENTION

The Gravity Field Energy Storage & Recovery System [GFESRS] Invention is a mechanical, electrical and electronic system that can store energy from a variety of sources. The energy is directed at a mechanical/electrical arrangement designed to raise a large massive object in a gravitational field, storing the energy as potential energy in the field.

The Force of Gravity is described as the mutual physical attraction which every particle in the universe has with every other particle in the universe. Newton discovered the universal law of gravitation in the year 1666 and described the force of gravity as

$F = \frac{{GM}_{a}M_{b}}{r^{2}}$

Where M_(a) and M_(b) are the masses of two particles, r is the distance between the particles, and G is a constant of proportionality. The constant G was first measured by Cavendish in 1771 and the accepted value today is

G=6.67×10⁻¹¹Nm²/kg²

A large ensemble of particles such as a planet, acts as an aggregated single object with a mass equal to the sum of the masses of the particles, and the force of gravity directed at the center of mass of the ensemble. Thus, the force of gravity upon an object near the surface of the Earth is

$F = \frac{{GM}_{e}m}{r^{2}}$

Where M_(e) is the mass of Earth taken as 5.98×10²⁴ kg, m is the mass of an object infinitesimally less massive than earth, and r is the distance between their centers of mass. The force is direct toward the center of the earth.

The acceleration due to gravity is

$\begin{matrix} {a = \frac{F}{m}} \\ {= \frac{{GM}_{e}}{r^{2}}} \\ {= {\sim {9.8\mspace{14mu} m\text{/}s^{2}\mspace{14mu} {or}}\mspace{14mu} \sim {32\mspace{14mu} {{ft}.\text{/}}s^{2}}}} \end{matrix}$

and interestingly, is independent of the mass of the object. This is the acceleration of gravity near the surface of the earth, which is usually denoted with a lower case italic g.

We calculate the change in g with increasing altitude, such

${g(r)} = \frac{{GM}_{e}}{r_{2}}$ $\begin{matrix} {{\Delta \; {g(r)}} = {\frac{d\; g}{dr}\Delta \; r}} \\ {= {{- \frac{2{GM}_{e}}{r^{3}}}\Delta \; r}} \\ {= {{- \frac{2g}{r}}\Delta \; r}} \end{matrix}$ $\frac{\Delta \; g}{g} = {- \frac{{2\Delta \; r}\;}{r}}$

and the fractional change is

At the earth's surface where r=6×10⁶ m and so g increases one part per million for every increase in altitude of 3 meters. This insignificant change is very important in considering the present invention since the efficiency of the energy storage does not change in relation to the state of charge.

Aristotelian mechanics, which was accepted for thousands of years, believed that a force was necessary to maintain a body in uniform motion. Newton, through experimentation found rather, that a force acting upon a body accelerates the body according to his famous 2^(nd) Law

The law in one dimension Can be integrated as

$F = {\frac{d\;}{dt}{Mv}}$ ${F(x)} = {m\frac{dv}{dt}}$ ${m{\int_{x_{a}}^{x_{b}}{\frac{dv}{dt}\ {x}}}} = {\int_{x_{a}}^{x_{b}}{{F(x)}{x}}}$

And after a formal procedure we find that

½mv _(b) ²−½mv _(a) ²=∫_(x) _(a) ^(x) ^(b) F(x)dx

where the term ½mv² is known as the kinetic energy and the right hand side is called work as the particle moves and changes velocity from a to b. In shorthand we say

K _(b) −K _(a) =W _(ba)

This formula is known as The Work-Energy Theorem in one dimension.

In practice we see that a canon ball traveling at high velocity may hit the hull of a ship and its velocity reduces to zero. It is the change in velocity which imparts the energy and does work on the hull. We also see that the velocity the canon ball, instead of being supplied by the expanding gasses in the canon could be supplied by a drop from a vertical height. The canon ball dropped from rest at a given height h above the ground will deliver a kinetic energy to do work on the ground in proportion to its height above the ground. We can call this a potential energy which can be released at will. It will require work to elevate the canon ball to its prearranged height. As it turns out the potential energy is equal and opposite the kinetic energy. We say

E=K+U

Where U denotes the potential energy of the system and E is the total mechanical energy of the system which is always constant since mechanical energy is conserved. Thus, as a mass at rest at a given height represents a potential energy, gravity will accelerate the mass and convert it to kinetic energy as the potential energy is reduced.

The Gravitational Energy Field Storage & Recovery System [GEFSRS] Invention operates within gravitational fields. These gravitational fields can be naturally occurring on planets and related celestial bodies.

When we do work to separate masses that are gravitationally attracted to each other we create a form of potential energy. This invention shows how to harness these forces to store energy and then recover this stored energy on demand.

We harness energy from a variety of sources to perform the work of repositioning the mass in the gravitational field driving the mass opposite the force vector of the gravitational attraction. This allows us to increase the potential energy in the system. Once energy is stored by the repositioning of the mass, we have the ability to recover the energy immediately or to store it indefinitely. The potential energy will remain intact indefinitely if the positioning apparatus remains intact. Once stored, maintaining this energy is lossless for an indefinite period of time unlike battery systems. This is the energy storage phase. Unlike battery systems, energy storage can be implemented incrementally up to the storage limit of the system, regardless of the state of charge or history of the system, without loss of efficiency.

The stored energy can be released and recovered by controlling the acceleration of the mass as the potential energy becomes kinetic energy. This kinetic energy can be converted to a plurality of useful energy forms. These energy forms include electrical, pneumatic, hydraulic and other forms.

Once we have secured the initial energy storage we can chose to

-   -   1. Add energy to the system     -   2. Keep the energy stored     -   3. Release the energy from the system.

The energy storage phase can be repeated with random or continuous amounts of energy until the GEFSRS embodiment reaches it energy storage limits. The stored energy can remain for indefinite periods of time without loss to the stored potential energy.

The stored energy can be released by controlling the acceleration of the Mass to the Earth. The conversion of the stored energy as potential energy becomes kinetic with the start of the release cycle. This kinetic energy can do work and the work can create a plurality of energy forms. These energy forms can be electrical, pneumatic, hydraulic power, or other forms.

General System Configuration

In the embodiment of the Elevator Shaft Example [ESE] we refer to the system depicted in FIG. 2. ESE shows photovoltaic solar panels to represent a plurality of energy sources. Energy can be harnessed from power sources such as:

-   -   1. electromechanical     -   2. geothermal     -   3. wind     -   4. ocean tidal     -   5. ocean current     -   6. ocean wave     -   7. ocean thermal     -   8. nuclear fission     -   9. nuclear fusion     -   10. solar     -   11. chemical reactions     -   12. pneumatic     -   13. hydraulic     -   14. mechanical     -   15. others

One or more of these forms of energy will be employed to drive the mass repositioning in the energy storage cycle. In the ESE example any of these forms of source energy are converted into electrical energy. This electrical energy is used to drive an electrical motor/generator. The motor/generator is operated in motor mode. In motor mode the system delivers electrical energy to the motor generator that turns a shaft. This shaft is used to create mechanical energy.

This mechanical energy is used to drive an energy conversion apparatus. The Energy Conversion Apparatus [ECA] in the ESE example is a gear box providing the proper gear ratios to operate in the three modes: supply energy to the system, store the energy, recover the energy from the system.

Electrical energy selected, processed, and managed is converted to mechanical energy by the use of an electrical motor/generator. The size of this motor allows it to drive the ECA. The ECA drives the main shaft. The main shaft is connected to the mass coupler. The mass coupler is connected to the massive object. The described apparatus repositions the mass of the massive object by lifting it in the elevator shaft to the upper limit in the elevator shaft.

In any desired position the massive object can be locked in position. By locking the position of the massive object no energy is required or lost during the storage cycle regardless of duration.

Having repositioned the massive object to the top of the elevator shaft we have two options that can be chosen. Keep the energy stored by not moving the massive object. Release the massive object in the elevator shaft to generate the required energy. After the desired energy storage duration has been completed it is time to release the energy that has been stored. The release cycle begins with the configuration of the system for energy generation.

The proper mechanical, hydraulic and electrical and system parameters are satisfied. Once satisfied the release and generation moves to the release of the locking mechanism.

With the release of the locking mechanism the management of the massive object is under the control of the mechanical, hydraulic and electrical systems. These systems are configured so the proper counter EMF (electro motive force) is electrically applied to the motor/generator in generator mode of operation. The application of the counter EMF/electrical load coincides with the completion of the following sequence of system operation.

The GEFSRS system delivers the proper mechanical load to allow the controlled falling of the massive object to turn the Main Shaft in the opposite direction of the energy storage cycle. The main shaft rotation drives the Energy Conversion Apparatus [ECA]. The rotation of the ECA drives the proper rotation of the Motor/Generator Shaft. The rotation of the motor/generator in generator mode generates electricity that exceeds the counter EMF/electrical load.

This energy release cycle and conversion process delivers electrical power to drive a load until the massive object has reached is resting state. When the massive object is at its resting state the energy storage cycle can be started. Or the massive object can remain in the resting state.

These cycles of

-   -   1. Adding energy to the system     -   2. Keeping the energy stored     -   3. Releasing the energy from the system.         are sequenced based on the system operators commands. These         cycles are repeated in any order required to operate the         invention.

FIGS. 1-4

-   -   1) SOLAR ARRAY: Delivers electric energy to the building.         Alternative electrical energy sources may include but are not         limited to; hydroelectric, wind, ocean tidal, ocean current, or         local power grid.     -   2) ELECTRICAL AND ELECTRONIC INTERCONNECT: Interconnect from         Solar Array 1 to System Electronics Control Unit 3. Provides         energy transfer to the storage system and contains electronic         sensor signal paths including contact closures and sensor data         delivering information, commands, and signals, to operate any         and all components of the system.     -   3) SYSTEM ELECTRONICS CONTROL UNIT: Manages the electrical         energy from the plurality of sources which may be used at         different times of day or night, characterized by parameters         such as load characteristics and weather.     -   4) ELECTRIC MOTOR/GENERATOR: An electric motor with         reconfigurable armature windings is used as both motor and         generator. In motor mode it is used to reposition the mass in         the gravitational field in the energy storage cycle. In         generator mode it is used to recover energy as the mass is         released in a controlled acceleration. The output of the         Electric Motor/Generator will connect to the System Electronics         Control Unit 3 via Electrical and Electronics Interconnect 3.     -   5) ELECTRIC MOTOR/GENERATOR SHAFT: Electric Motor/Generator         Shaft couples Electric Motor/Generator 4 to Energy Conversion         Apparatus 6.     -   6) ENERGY CONVERSION APPARATUS: The Energy Conversion Apparatus         (transmission) couples the Electric Motor/Generator Shaft 5 to         the Main Shaft 7. The embodiment described in the drawing shows         a gear reduction system. This transmission allows the proper         gear ratios to be configured to optimize the load on the system         during charging and recovery cycle.     -   7) MAIN SHAFT: The Main Shaft 7 bears the load of the Mass 9 via         Cable 8 which spools around the shaft. The main shaft rotates         one direction in the charging cycle and reverses during energy         recovery.     -   8) CABLE: Cable 8 couples Main Shaft 7 to Mass 9. Rotation of         Main Shaft 7 spools Cable 8 changing its length.     -   9) MASS: Mass 10 is any massive object of any size or weight.     -   10) PULLEY: Pulley 10 and Cable 8 comprise a block and tackle         system configured to optimize load on the system during charging         and recovery phases. Together they couple Electric         Motor/Generator Shaft 5 to Mass 9.     -   11) RACK: The Main Shaft 7 couples to Buoyant Object 12 through         Rack 12. Pinion on Main Shaft 7 and Rack 12 form a rack and         pinion system such that the rotation of Main shaft 7 causes a         lowering or raising of Buoyant Object 12.     -   12) BUOYANT OBJECT: The Buoyant Object 12, which floats in         water, is forcibly submerged into water by Rack 11.     -   13) WATER SURFACE: Depicts the surface of the body of water.     -   14) SEABED: Depicts the surface of the Earth below the water.     -   18) DIESEL TRACTOR: Diesel tractor energy source coupled to the         system by means of power take-off shaft providing rotational         shaft horsepower to charge the system.     -   16): PTO SHAFT: Direct drive from Diesel engine provides shaft         horsepower to the diesel tractor to the Energy Conversion         Apparatus.     -   17) CONVERTER CONTROLLER APPARATUS: Converter Controller         Apparatus 20 couples PTO Shaft 16 to Main Shaft 7 via Cable 8         which spools at the output of the Controller Apparatus. The         transmission attains the proper gear reduction ratio to couple         the load efficiently to the power source. Converter Controller         Apparatus 17 contains locking system to maintain Mass 9 in         position during storage phase, and to release mass during         recovery stage.     -   18) ELECTRIC GENERATOR: Electric Generator 18 is coupled to         Shaft 7 and converts shaft horsepower to electricity during         recovery phase. The electric output of Generator 18 is available         to feed remote installations such as oil pump pictured. 

We claim:
 1. An energy storage and recovery system that operates in a gravitational field that consists of: (a) An energy source (b) An energy conversion apparatus that converts energy as in (a) to mechanical energy (c) A massive object (d) A mechanical arrangement that repositions massive object (c) into a state of higher potential energy (e) A mechanical arrangement that maintains mass (c) in a state of higher potential energy as in (d) for an indefinite period of time (f) A mechanical arrangement that controls and converts kinetic energy as in (f) to a plurality of energy forms including, but not limited to, electrical, rotational, pneumatic, and hydraulic
 2. An energy storage and generation system as in claim 1 where the energy source (a) is an electrical energy source and the energy conversion apparatus (b) is an electric motor/generator.
 3. An energy storage and generation system as in claim 1 where the energy source (a) is pneumatic and the energy conversion apparatus (b) is a pneumatic motor.
 4. An energy storage and generation system as in claim 1 where the energy source (a) is hydraulic and the energy conversion apparatus (b) is a hydraulic motor.
 5. An energy storage and generation system as in claim 1 where mechanical arrangement (d) incorporates an electric generator.
 6. An energy storage and generation system as in claim 1 where mechanical arrangement (d) incorporates a pneumatic pump/motor.
 7. An energy storage and generation system as in claim 1 where mechanical arrangement (d) incorporates a hydraulic pump/motor
 8. An energy storage and recovery system that operates in a gravitational field that consists of: (a) An energy source (b) An energy conversion apparatus that converts energy as in (a) to mechanical energy (c) A buoyant object (d) A mechanical arrangement that repositions buoyant object (c) into a state of higher potential energy (e) A mechanical arrangement that maintains buoyant object (c) in a state of higher potential energy as in (d) for an indefinite period of time (f) A mechanical arrangement that releases mechanical arrangement as in (e) on demand causing buoyant object (c) to gain kinetic energy (g) A mechanical arrangement that controls and converts kinetic energy as in (f) to a plurality of energy forms including, but not limited to, electrical, rotational, pneumatic
 9. An energy storage and generation system as in claim 8 where the energy source (a) is an electrical energy source and the energy conversion apparatus (b) is an electric motor/generator.
 10. An energy storage and generation system as in claim 8 where the energy source (a) is pneumatic and the energy conversion apparatus (b) is a pneumatic motor.
 11. An energy storage and generation system as in claim 8 where the energy source (a) is hydraulic and the energy conversion apparatus (b) is a hydraulic motor.
 12. An energy storage and generation system as in claim 8 where mechanical arrangement (d) incorporates an electric generator.
 13. An energy storage and generation system as in claim 8 where mechanical arrangement (d) incorporates a pneumatic pump/motor.
 14. An energy storage and generation system as in claim 8 where mechanical arrangement (d) incorporates a hydraulic pump/motor 